The closest prior art known to applicants is contained in the following references:
Great Britain Pat. No. 1,260,521 to Allen & Hanburys Ltd. published Jan. 19, 1972.
U.S. Pat. No. 4,000,193 to Allen & Hanburys Ltd. published Dec. 28, 1976.
U.S. Pat. No. 3,644,353 to Allen & Hanburys Ltd. published Feb. 22, 1972.
U.S. Pat. No. 3,705,233 to Allen & Hanburys Ltd. published Dec. 5, 1972.
U.S. Pat. No. 3,732,300 to Allen & Hanburys Ltd. published May 8, 1973.
U.S. Pat. No. 4,012,444 to Allen & Hanburys Ltd. published Mar. 15, 1977.
U.S. Pat. No. 4,066,755 to Allen & Hanburys Ltd. published Jan. 3, 1978.
U.S. Pat. No. 3,883,560 to Richardson-Merrell Inc. published May 13, 1975.
Belgian Pat. No. 739,678 to Continental Pharm. published April 1, 1970.
None of these references discloses the specific compound of the present invention which is distinguishable over the prior art in view of the unexpected superior properties of said compound which are discussed in detail hereinafter.